Plans to add a hormone which suppresses hunger to baby formula food is unlikely to work say experts.

University of Buckingham researchers are looking at adding leptin to formula milk to curb future over-eating.

But experts said the work detailed in Chemistry and Industry was "wildly optimistic science fiction" and questioned testing leptin on babies.

Babies fed with formula grow more quickly than breast-fed babies - who have a lower risk of obesity as adults.

'Adding something back'

The work into the effect of leptin, a hormone produced in the brain throughout life, is being carried out at the Clore Laboratory at the University of Buckingham.

Without evidence that this works in humans, it is pure flight of fancy that those consuming leptin from infancy will never get fat

Dr Ian Campbell, Weight Concern

The team, led by Dr Mike Cawthorne, are looking at adding leptin to formula milk and other foods.

They have already carried out a study where leptin was given to pregnant rats, leading to a lifelong impact on their offspring's propensity to obesity.

Even those fed a fat-laden diet stayed slim, while offspring from untreated rats gained weight and developed diabetes.

Research into the effect of the hormone on human appetite has so far proved disappointing, with people soon seeming to resist its hunger-quenching effects.

But Dr Cawthorne said providing leptin early effectively "hard-wires the body's energy balance".

He added: "The supplemented milks are simply adding something back that was originally present - breast milk contains leptin and formula feeds don't."

'Altering the brain'

However, a number of experts have criticised the concept of adding leptin to formula milk.

Steve O'Rahilly, professor of clinical biochemistry and medicine at the University of Cambridge said: "Several researchers have suggested that exposing animals to higher leptin levels during early life might have long-lasting benefits in terms of protection against later obesity.

"But this still needs to be firmed up.

"The notion that leptin in baby milk will prevent human obesity is currently in the realms of wildly optimistic science fiction."

He said: "The concept that adding something to a food that could permanently alter brain development is exciting but at the same time so scary that it would mean a wholly new approach about how such treatments can be tested and approved for use.

"And would the first trials be in newly born children?"

Dr Ian Campbell, honorary medical director of the charity Weight Concern said: "Without evidence that this works in humans, it is pure flight of fancy that those consuming leptin from infancy will never get fat.

"I'd be surprised if this product could be advertised or marketed with these extraordinary claims."

He added: "To date, leptin has proved to be a great disappointment. Most of us have plenty, and true deficiencies are rare.